The present invention relates to the contact-free measurement of the distance of an object according to the principle of laser triangulation, according to the introductory part of patent claim 1.
Such a method is known per se and is applied in many aspects. A laser beam is directed perpendicularly on the measuring object and here produces a point of light (diffuser Reflex). Laterally next to the laser a line-like sensor is arranged (PSD or CCD). The line-like sensor consists of, as is known, a multitude of individual light-sensitive elements of a low dimension, which are electronically scanned. The light point on the measuring object is imaged on the line-like sensor via suitable sensor optics. Depending on the distance between the measuring system and the object the position of the imaged light point changes on the sensor line. The position on the line is thus a measure for the distance in each case. The output signal of the sensor line may as a result serve as a distance signal from which then in a suitable manner the distance is computed.
The known method requires that the laser beam is directed perpendicularly onto the measuring object so that with a changing distance no parallax displacement of the projected laser point takes place. Such an arrangement has the disadvantage that the measuring apparatus must be arranged in the measuring axis. Such an arrangement in many cases is not desirable or not possible, for example when in the measuring axis there is located another object or when the position measurement of objects which move towards the measuring system, is carried out at a certain location, and then move further in the same direction. This for example is the case with the distance measurement of steel slabs on a roller table.